screencast_start

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The only annotation is readOnlyHint=false, so the description carries most of the burden. It establishes recording of the target page but says nothing about the recording continuing until screencast_stop, where output is written (beyond the schema's filePath note), or any disk/resource implications of an in-progress capture.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single front-loaded sentence with zero filler. It is efficient, but the terseness borders on under-specification for a stateful operation that requires a paired stop call.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Two simple parameters, no output schema, and a thin annotation set — the description is adequate to identify the action but leaves out lifecycle context (stop requirement, output location, page prerequisite) that an agent needs to drive the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with both pageId and filePath documented including the mkdtemp fallback behavior. The description adds nothing beyond the schema, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Specific verb + resource + scope: 'Starts recording a screencast (video) of the target page.' It is clearly distinguishable from the sibling screencast_stop by the verb 'starts', though it never names that counterpart explicitly.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

No when-to-use guidance, no prerequisites (e.g., that a page must be selected), and no mention of the screencast_stop sibling that must eventually be called. Usage is only inferable from the verb.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.